Background art related to the present invention will be described by taking a hydraulic excavator as an example.
FIG. 7 illustrates an upper slewing body mounted on a lower propelling body in a hydraulic excavator. The upper slewing body comprises: an upper frame 1; an engine room 2; an engine 3 provided inside the engine room 2; a hydraulic pump 4; an exhaust-gas-purification device (DPF: Diesel Particulate Filter, also called “exhaust gas filter” or “soot purifying device”) 5 as one type of exhaust-gas-aftertreatment device; a heat exchanger 6; a cooling fan 7; a table 9 for supporting the exhaust-gas-purification device 5; and a guard panel 12.
The upper frame 1 has a front end (in FIG. 7, a left end) to which a non-illustrated work attachment comprising a boom, an arm and a bucket is attached, and a rear end on which the engine room 2 is formed. The engine 3 is provided inside the engine room 2 in a posture of extending in a right-left direction of the engine room 2. The hydraulic pump 4 is disposed on one side of the engine 3 in the right-left direction, e.g., on a right side (in FIG. 7, an upper side) of the engine 3, and connected to an output shaft of the engine 3. The exhaust-gas-purification device 5 is installed so as to extend in a front-rear direction across and over the hydraulic pump 4. The heat exchanger 6 and the cooling fan 7 are installed on a left side of the engine 3.
The exhaust-gas-purification device 5 is connected to the engine 3 via a flexible exhaust pipe 10, to remove harmful substances, particularly, PM (Particulate Matter) such as soot, contained in exhaust gas of the engine 3 to purify the exhaust gas, discharging the purified exhaust gas to outside via an exhaust stack 11.
The table 9 is provided above the upper frame 1 via a support leg 8, and the exhaust-gas-purification device 5 is placed on the table 9.
The guard panel 12 is provided on the upper frame 1 to define the engine room 2, as illustrated in FIG. 8, and the engine 3 and the hydraulic pump 4 are housed inside the guard panel 12. The guard panel 12 has a maintenance port 13 which is opened in a right sidewall thereof to allow maintenance of a hydraulic pump 4 (including a regulator 4a provided on an upper surface of the pump) to be performed from outside therethrough.
In the engine room 2, there is provided a partition wall 14 so as to shut off between the exhaust-gas-purification device 5 and the hydraulic pump 4. The partition wall 14 defines, on a right side thereof and just above the hydraulic pump 4, a maintenance space for allowing maintenance of the hydraulic pump 4 to be performed through the maintenance port 13.
However, in the case of a need for enhancing exhaust gas purification performance, there is possibility of providing a NOx-reducing catalyst 15 for reducing NOx contained in exhaust gas, one type of exhaust-gas-aftertreatment device, as additional equipment in side-by-side relation with the exhaust-gas-purification device 5, as described in the following Patent Document 1, which may exert an influence on the maintenance of the hydraulic pump 4.
More specifically, in the case of adding the NOx-reducing catalyst 15 to the structure illustrated in FIG. 8, it is conceivable that the NOx-reducing catalyst 15 is installed on a right side of (a side closer to the maintenance port 13 with respect to) the exhaust-gas-purification device 5 in side-by-side relation with the exhaust-gas-purification device 5, and connected to the exhaust-gas-purification device 5 via a connection pipe 16, as illustrated in FIG. 9A. In this case, there is provided a table 17 which is so long in the right-left direction as to extend across the exhaust-gas-purification device 5 and the NOx-reducing catalyst 15 while being supported by a support leg 18. This table 17 additionally serves as a fire-protecting partition wall. In some cases, each of the table 17 and the support leg 18 is separately divided into two separate portions: one for the exhaust-gas-purification device and the other for the NOx-reducing catalyst.
In this arrangement, i.e., in an arrangement where the exhaust-gas-purification device 5 and the NOx-reducing catalyst 15 are arranged side-by-side on the same horizontal plane at respective relatively low positions as illustrated in FIG. 9A, the table 17 supporting them closes up an upper space of the hydraulic pump 4, thereby preventing maintenance requiring access to the hydraulic pump 4 from thereabove, particularly, inspection or replacement of the regulator 4a of the hydraulic pump 4, from being performed, unless the table 17 and the NOx-reducing catalyst 15 are removed.
The maintenance space just above the hydraulic pump 4 can be formed, for example, by raising an overall position of the exhaust-gas-purification device 5 and the NOx-reducing catalyst 15, as illustrated in FIG. 9B. This arrangement, however, requires an increase in length of the flexible exhaust pipe 10 for interconnecting the engine 3 and the exhaust-gas-purification device 5, involving an increase in cost. Besides, raising the position of the exhaust-gas-purification device 5 gives rise to a need for forming a portion (in the illustrated embodiment, a right end) 12a of the top wall of the guard panel 12 corresponding to an installation position of the exhaust-gas-purification device 5 and the NOx-reducing catalyst 15, into a shape protruding upwardly, as illustrated in FIG. 9B. The protruding portion 12a, requiring a large size in a width direction (right-left direction) for covering both of the exhaust-gas-purification device 5 and the NOx-reducing catalyst 15, significantly narrows operator's rearward visibility (exactly, visibility in an obliquely rearward direction). The NOx-reducing catalyst 15 is equipment to be additionally provided according to the need for enhancing exhaust gas purification performance; however, even in the case of not providing the NOx-reducing catalyst 15, there also exists a need for improving maintainability of the hydraulic pump 4 while ensuring an installation area for the NOx-reducing catalyst 15.